For some payment P, you want 27000 = P + I 27000 = P + Prt . . . . substituting the formula for I 27000 = P(1 + .15·10/12) = 1.125 Then 27000/1.125 = P = 24000
Overestimate because then the gardener could possibly save the left overs in case they get a chance to use it or they could give it to someone who may need it.